Before you start you might need to consider your disk configuration
to sort out a quirk in SCSI-ID to SD-UNIT mapping that exists on
Sun SPARCstations.

Upon leaving the factory, SunOS and the OpenBOOT ROM map according to
this table:

    SCSI-ID ->	SunOS SD-UNIT
    0		sd3
    1		sd1
    2		sd2
    3		sd0
    4		sd4
    5		sd5
    6		sd6

Unlike SunOS and the OpenBOOT ROM, a generic OpenBSD kernel numbers
SCSI drives sequentially as it finds them.  The drive with the
lowest SCSI-ID will be called sd0, the next one sd1, etc.

This is mostly a non-issue if you have only one drive on your system,
but can get confusing if you have multiple drives (unless you choose
to use DUIDs to access partitions).  If you plan to eliminate SunOS
altogether it may be best to correct the SCSI-IDs of your drives,
while if you plan to leave SunOS installed, it may be better to
install OpenBSD on a drive with SCSI-ID 1 or 0.

Older OpenBoot proms (versions 1.x) provide an environment variable,
sd-targets, that controls the drive<->SCSI-ID mapping; you can change
this to reflect the natural ordering or just set the boot related
variables to boot from the correct drive, whatever the numbering. Its
default-value is ``31204567'', which means unit 0 and 3 are exchanged.
To revert to the ``normal'' behaviour, enter the following command:

    ok setenv sd-targets 01234567

Your OpenBOOT ROM may need some setup.  If you are running OpenBSD on
a sun4c, sun4e or sun4m system, the ROM must be set to "new" command
mode.  If your machine comes up and gives you a `>' prompt instead of
`ok', type:

    > n
    ok setenv sunmon-compat? false
    ok

This is needed because OpenBSD relies on the behaviour of the "new" command
mode.  OpenBSD will not boot correctly on sun4c, sun4e or sun4m systems that
are not running in "new" command mode.  The sun4 systems such as the 4/110,
4/200, and 4/300 system do not have a "new" command mode, and will work
fine as-is.


Also, you cannot use the security modes of the SPARC OpenBOOT ROM.
Make sure that the ROM security modes are disabled:

    ok setenv security-mode none

To disable automatic boot use the following command:

    ok setenv auto-boot? false

and then to enable it later use:

    ok setenv auto-boot? true

or on an installed system use the eeprom(8) command:

    # eeprom 'auto-boot?=true'

